The present invention relates to in-vivo measurement systems in general and specifically to a device for internal measurements of electrical characteristics of a biological lumen.
Physiological tissues are typified by specific electrical impedance characteristics. Variance in types of epithelial tissue, for example, may be recognized by differences in electrical characteristics (Gonzales-Correa CA et al., xe2x80x9cVirtual biopsies in Barrett""s esophagus using an impedance probexe2x80x9d, Annals of NY Academy of Sciences, Vol. 873, April 1999, pp. 313-321).
Changes of this characteristic impedance can provide essential information about the tissue, and the entire organism. This concept has been the springboard for a great deal of research into predicting pathological conditions, especially cancer (Blad B and Baldetorp B, xe2x80x9cImpedance spectra of tumor tissue in comparison with normal tissue: a possible clinical application for electrical impedance tomographyxe2x80x9d, Physiological Measurements, Vol. 17 Suppl 4A, November 1996, pp. 105-115). For example, the early detection of colon cancer may be possible by examining differences in electrical properties of surface colonic epithelium (Davies R J et al., xe2x80x9cColonic epithelial impedance analysis in a murine model of large-bowel cancerxe2x80x9d, Archives of Surgery, Vol. 124(4), April 1989, pp. 480-484). These measurements are generally done using an endoscope or a probe with electrodes at the end.
Similarly, breast cancer may be predictable based on impedance differences in normal and pathological tissue (Chauveau N et al., xe2x80x9cEx vivo discrimination between normal and pathological tissues in human breast surgical biopsies using bioimpedance spectroscopyxe2x80x9d, Annals of NY Academy of Sciences, Vol. 873, April 1999, pp. 42-50; and Jossinet J, xe2x80x9cA Variability of impedivity in normal and pathological breast tissuexe2x80x9d, Medical and Biological Engineering and Computing, Vol. 34(5), September 1996, pp. 346-350).
Many other conditions may be predictable based on electrical impedance changes. For example, esophagus impedance may be related to Barrett""s esophagus, a disorder in which the normal squamous mucosa of the esophagus is replaced by columnar epithelium (Gonzales-Correa C A et al., xe2x80x9cVirtual biopsies in Barrett""s esophagus using an impedance probexe2x80x9d, Annals of NY Academy of Sciences, Vol. 873, April 1999, pp. 313-321). Changes in oral impedance may be related to changes in oral mucosa (Nicander B L et al., xe2x80x9cElectrical impedance. A method to evaluate subtle changes of the human oral mucosaxe2x80x9d, European Journal of Oral Science, Vol. 105(6), December 1997, pp. 576-582). Other diagnoses using this principle include tissue injury (Paulsen K D et al., xe2x80x9cIn vivo electrical imedance spectroscopic monitoring of the progression of radiated-induced tissue injuryxe2x80x9d, Radiation Research, Vol. 152(1), July 1999, pp. 41-50), lung ventilation (Frerichs I et al., xe2x80x9cMonitoring regional lung ventillation by functional electrical impedance tomography during assisted ventillationxe2x80x9d, Annals of NY Academy of Sciences, Vol. 873, April 1999, pp. 493-505), and ischemic tissue (Casa O et al., xe2x80x9cIn vivo and in situ ischemic tissue characterization using electrical impedance spectroscopyxe2x80x9d, Annals of NY Academy of Sciences, Vol. 873, April 1999, pp. 51-58).
Measurement of impedance characteristics of tissue is typically accomplished through the use of a probe with electrodes or by implanting electrodes (Lehrer A R et al., xe2x80x9cElectrical resistance of genital tissues during reproductive events in cows, and its possible on-farm applications: A reviewxe2x80x9d, Wiener Tierarztliche Monatsschrift, Vol. 78, 1991, pp. 317-322). The electrodes may be attached to the end of an enteroscope for measurements of the intestines. Additional techniques have been developed as well. One of these techniques is termed xe2x80x9celectrical impedance tomographyxe2x80x9d, or EIT (Brown B H et al., xe2x80x9cApplied potential tomography: possible clinical applicationsxe2x80x9d, Clinical Physiology and Physiological Measurements, Vol. 6(2), May 1985, pp. 109-121). This method involves resistivity distribution changes following ingestion of conducting or insulating fluids. In addition, body composition may be analyzed by total body conductivity (Galvard H, et al., xe2x80x9cDifferences in body composition between female geriatric hip fracture patients and healthy controls: body fat is a more important explanatory factor for the fracture than body weight and lean body massxe2x80x9d, Aging (Milano), Vol. 8(24), August 1996, pp. 282-286; and Yasiu T, et al., xe2x80x9cBody composition analysis of cachetic rabbits by total body electrical conductivityxe2x80x9d, Nutrition and Cancer, Vol. 32(3), 1998, pp. 190-193).
The present invention describes apparatus and method for measuring electrical characteristics of a biological lumen.
There is thus provided, in accordance with a preferred embodiment of the present invention, apparatus for measuring electrical characteristics of biological tissues which includes a capsule with an external surface having openings, a plurality of electrodes located within the openings, and a processor in communication with the electrodes for generating electrical characteristics.
The apparatus may further include an imager for imaging an area of interest within the biological tissue.
The capsule may be autonomous, and it may be introduced by swallowing or by placing it in a desired location in the body.
The electrical characteristics may include impedance or conductivity values or any other relevant electrical characteristics as determined by the user. The biological tissue may be the small intestine or the interior of any portion of the digestive tract.
The plurality of electrodes includes at least two electrodes. Electrodes may be metallic rings, where the openings are slits, or they may be metallic spheres or cups, where the openings are round. Electrodes may protrude through the openings or they may be flush with the external surface of the capsule.
The invention further describes a method for measuring electrical characteristics of a digestive tract in a body, including the following steps: introducing into the digestive tract an autonomous electrode configuration, selecting sets of electrodes for measurement, introducing a current into the selected electrodes, collecting electrical data from selected electrodes, and calculating electrical characteristics from collected data. The autonomous configuration may be located on the external surface of a capsule, and it may be introduced into the digestive tract by swallowing.
A further embodiment of the present invention includes the step of transmitting the electrical characteristics to a wireless receiver outside the body.
In one embodiment of the present invention the step of collecting includes obtaining a voltage between the two selected electrodes. Electrical characteristics may be impedance or conductivity values.
Furthermore, one embodiment of the present invention includes the step of measuring a time parameter. Another embodiment further includes the step of determining a distance within the digestive tract.